SO2 chemisorption on oxygenated Pt(111) enormously enhances the dissociative chemisorption and subsequent combustion of propane. This activation of the metal surface is induced by an adsorbed sulfoxy species which is formed at >220 K. In the absence of adsorbed SO2 the sticking probability of propane is immeasurably small. However in the presence of SO2, the precursor-mediated initial sticking probability rises from similar to 0.02 at 300 K to similar to 0.15 at 160 K : all of the hydrocarbon is irreversibly adsorbed. n-Butane and n-heptane show similar behavior; methane and ethane do not.